The present invention relates to improvements in pumps for liquids, particularly for pumps useful for pumping in difficult situations.
A primary application of the present invention relates to pumping an oil/grease component from effluent from kitchens. Typical modern restaurant kitchens produce a large volume of waste water containing various components in addition to water. These components include, food solids and, of particular concern, oils and greases. Oils and greases cause problems in sewage treatment plants so that the sewage treatment authorities encourage, and often require, that these components, generally referred to herein as "oil/grease," be removed from the effluent. In addition, these removed oil/grease components can be useful if separated from the water promptly before the oil/grease components become rancid.
Various devices have been disclosed for removing oil/grease from kitchen waste, such as those shown in U.S. Pat. No. 4,268,396 to Lowe and U.S. Pat. No. 4,235,726 to Shimko. Also, well known in this industry are the commercial products of the Lowe Engineering Company of Uncoln Park, N.J. and Thermaco, Inc. of Asheboro, N.C. These products generally operate by passing an oleophilic planar surface through the top surface of the oil/grease resting on a body of relatively still effluent. The oil/grease, having risen to the top of the still effluent, adheres to the oleophilic surface and can be scraped off.
However, there are still problems of solids floating of the surface which can interfere with the operation of the oleophilic surface and the scraper. Also, the throughput capacity of the prior art devices is somewhat limited, since the amount of oil/grease which can be removed by a given oleophilic surface is limited.
Furthermore, the oil/grease scraped from the oleophilic surface sometimes congeals and clogs the downstream piping. Accordingly, it would be helpful if positive pumping could be achieved, although conventional pumps can also be defeated by such congealed oil/grease.
Applicant's invention provides a pump that addresses these needs and also provides for an improved pump of general application having certain advantages.
Prior pumps of various designs can be defeated by attempting to pump liquids which contain the congealed or other solid matter, and the present invention provides a pump which does not suffer from these deficiencies.
Also, when pumping corrosive or hazardous liquids, in the past, there's been the problem of residual liquid remaining in the pump after a pumping session. The residual liquid remaining in the pump, acts as a reservoir of the hazardous or corrosive liquid, and is thus also contaminated.
Also, most prior pumps have required numerous moving parts, causing them to be expensive to manufacture and difficult to maintain. The present invention is not saddled with these drawbacks.
Also, typically the prior art pumps are of the substantial size, so that they are difficult to fit into small spaces from which it is desired to pump liquid. The present invention provides a pump which can be made small enough to be of virtually the same diameter as the liquid conveying line to be used with the pump, so that it can be used in such circumstances.
Finally, the present invention can be operated in a mode to provide a pump which meters precise quantities of liquid, unlike most prior art pumps.